Sir Martin resigned from WPP last April after the board investigated claims of misconduct, which he has denied.

He then took charge of a shell company, Derriston Capital, and turned it into S4 Capital, a “multinational communication services business”.

In July last year WPP threatened to take away his share awards when it turned out that both WPP and S4 were competing to buy Dutch firm Mediamonks, and it was thought Sir Martin was in breach of his confidentiality agreements.

S4 acquired Mediamonks later that month and WPP has not pursued any legal claims over Sir Martin’s bonus.

The share awards are estimated to be worth some £20m over five years to Sir Martin.